Wear reduction additives



P 7, 1955 D. E. JACOBSON ETAL 3,204,558

WEAR REDUCTION ADDITIVES 2 Sheets-Sheet 1 Filed Nov. 20, 1961 FIGS INVENTORS Dovid Esriel Jacobson y Shg Yngve Ek Attorneys P 1965 D. E. JACOBSON ETAL 3,204,558

WEAR REDUCTION ADDITIVES 2 Sheets-Sheet 2 Filed Nov. 20, 1961 PIC-l8 F/Gl/ "I, Lag in -$81: K

INVENTOR. Dovid Esriel Jacobson y Siig Yngve Ek United States Patent 3,204,558 WEAR REDUCTION ADDITIVES David Esriel Jacobson, Stockholm, and Stig Yngve Ek, Vallingby, Sweden, assignors, by mesne assignments, to Wegematic Corporation, New York, N.Y., a corporation of Delaware Filed Nov. 20, 1961, Ser. No. 153,299 Claims priority, application Sweden, Aug. 14, 1959, 7,582/59; Sept. 4, 1959, 8,199/59; Nov. 3, 1959, 10,259/59; Mar. 22, 1961, 3,034/61 23 Claims. (Cl. 102-38) This application is a continuation-impart of our copending applications Serial Nos. 46,008, 46,009 and 126,747. Applications Serial Nos. 46,008 and 46,009 are now abandoned and application Serial No. 126,747 is now Patent No. 3,148,620.

Certain of the concepts and of the subject matter disclosed in this application but not claimed herein are claimed in copending application Serial No. 377,278 filed June 23, 1964-.

This invention relates to compositions, and methods of applying the compositions for reducing erosion in a member subjected to hot flowing gases. More particularly, the present invention provides compositions and methods of reducing wear normally attendant with the use of known propellant charges in firearm barrels, and the description of the invention is here made in connection with this function. By cartridge is meant aca-se, capsule, shell or bag holding a propellant charge for a firearm; in small arms and some guns the cartridge also includes the projectile.

The problem of excessive barrel wear has existed throughout the history of firearms; however, it is today particularly critical due to the more powerful propellant charges in modern cartridges. For example, the present life expectancy of a gun barrel may be 250 rounds, after which time it must be replaced. This has the obvious disadvantage of impairing accuracy of the gun after several firings and also necessitates removal of the gun from service for the period of barrel replacement. By using the additive compositions of the present invention it has been discovered that the life of a barrel having reasonable accuracy may be extended tor the practical life of the gun in some instances; e.g., instead of being limited to 250 rounds, the capacity of a gun barrel may be increased to accurately firing 2000 or more rounds.

The cause of barrel wear is not fully understood, but it is thought to be due to melting, softening or chemical or physical deterioration of the barrel surface on firing, and a subsequent partial erosion of this soft layer by the out-flowing combustion gases.

Briefly, barrel wear is reduced by the preferred embodiments of the present invention by incorporating in the cartridge, a first material which upon firing of the cartridge will inhibit temperature and erosion wear on the gun barrel surface. It is thought this is accomplished by forming an erosion resistant layer on the barrel surface when the cartridge is fired. Also included is a second material which will produce gases relatively cool in comparison with the hot products of combustion of the main charge and which act to insulate the barrel forming a cool gaseous layer between the hot propellant gases and the barrel. The materials may be utilized with any conventional propellants to reduce the normal wear effects produced thereby.

Prior attempts to offset the deleterious effects of propellent charges on firearm barrels have includedthe use of ammonium carbonate in a cartridge as disclosed in Ice US. Patent No. 1,187,779 to Patten to produce relatively cool gases for surrounding the products of combustion of the main propellant charge and thereby protecting the barrel wall from the high temperature effects of such products. US. Patent No. 2,131,353 to Marsh discloses various additives for smokeless powder for forming .a deposit in the gun bore to protect the latter against the rusting effects of humidity and the residual products of combustion of the power remaining in the barrel, but not against the erosive effects caused by the combustion gases during firing. Therefore, while it has been proposed to form a rust resistant deposit and also to produce cool gaseous barrel insulation, the present invention provides protection against wear on metal members superior to prior art methods. Thus, this invention for the first time contemplates forming temperature and erosion resistant inhibitors to extend the life of firearm barrels and other metal members subjected to hot flowing gases. Moreover, this invention also provides gaseous insulation layers superior to such insulation disclosed by Patten by using more efficient materials, and in a much'simpler and more economical manner as will be described hereinafter.

Accordingly, it is an object of this invention to reduce the amount of wear in a member subjected to hot, rapidly flowing gases.

It is another object of this invention to reduce the erosion in a metal member such as a firearm barrel by incorporating erosion preventative material in the fire-arm cartridge comprising zinc or zinc compounds.

It is still a further object of this invention to reduce Wear on a metal member by incorporating material in a cartridge which will form, a temperature and erosion resistant layer, cool insulating gases, or both.

Another object of this invention is to provide novel arrangements of an additive layer with respect to a propellant charge.

A further object of this invention is to provide additive materials containing zinc for reducing wear in a gun barrel which are applied in a cartridge, around the propellant charge by being secured to the inner Wall of the cart-ridge case, to the textile or other like bag containing the propellant charge, or directly to the charge.

Still another object this invention is to provide an additive layer containing zinc for a cartridge which is simply and economically applied and which is retained in position by a suitable securing means.

A special advantage of the cartridge of the invention is the unchanged characteristics of the internal ballistics compared with the untreated charge. We have for instance found that muzzle velocity and pressure are unchanged.

Further objects and advantages will become apparent to those skilled in this art from the appended claims and following description of the invention and exemplifioations thereof, made in con-junction with the accompanying drawings showing preferred exemplary embodiments and wherein:

FIGURE 1 is a front elevation view, partly broken away, of a cart-ridge embodying the preferred additive of the present invention;

FIGURE 2 is a view of an unfolded sheet utilized in the cartridgeof FIGURE 1;

FIGURE 3 is a side elevation view of the sheet shown in FIGURE 2;

FIGURE 4 is an elevation view of a cartridge, partly broken away, illustrating a modification of the present invention;

FIGURE 5 is a front elevation view of a cartridge, I

partly broken away, illustrating another embodiment of the present invention;

FIGURE 6 is a front elevation view of a cartridge, partly broken away, illustrating a further modification of the present invent-ion; and,

'FIGURES 7-12 are also elevation view of cartridges partly broken away, illustrating further modifications of the present invention as will be described. It will be appreciated that the drawings herein illustrate diagrammatically the use of additives in accord with the present invention and that the proportions are not necessarily to scale.

It will be understood that the additive may consist of a layer forming material or a cool gas forming material alone. However, in accordance with the preferred embodiment of this invention, an additive containing zinc is incorporated in a cartridge which it is thought, produces on firing, a temperature and erosion resistant layer on the inner surface of a gun barrel by suspending a layer forming substance in the hot, rapidly flowing gases of the firearm. It is believed that the layer is comprised of nitrides, oxides or carbides, and that the layer protects the barrel from and is then partly removed by the hot combustion gases formed by the rear part of the charge. The additive may be applied in several ways, but in general it is preferred that the layer forming substance be dispersed in a continuous layer of the second substance around the propellant charge. By placing the additive substance around the charge a very good cool gaseous insulation layer is obtained and also the first substance will be readily and substantially uniformly carried into contact with the inner barrel surface by the combustion gases. The layer will resist action of the hot gases, and as will be described later, may result in as much as 90% or more reduction in normal wear in the barrel.

The first, or layer forming substance preferably comprises an element which can form a high melting nitride, oxide, or carbide and is one or more of the following: aluminum, boron, titanium, vandadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, uranium, zinc or thorium. Although it may be possible to use one of these elements by itself in the cartridge, an individual element may through combustion reaction with the propellant gases procure a combustion temperature appreciably above that of the hot flowing gases and if used as a powder additive, may actually increase barrel Wear. Therefore, it is generally preferable for the layer forming substance to be a compound which contains one or more of the above elements and which does not cause a rise in temperature of the combustion gases.

The following compounds have been found to give very good results in cartridges and it is thought that they may have a similar effect in other members particularly steel members subjected to hot rapidly flowing gases: 2. salt of aluminum and an inorganic acid, especially aluminum fluoride, hydrated aluminum fluoride (AlF 3H O), potassium titanium fluoride, chromium fluoride, vanadium pentoxide, titanium oxide (TiO- niobium oxide (Nb O tantalum oxide (Ta O tungsten oxide (W and especially the following zinc compounds: zinc oxide (ZnO), zinc sulphide (ZnS) zinc carbonate (ZnCO zinc phosphate (Zn (PO zinc fluoride (ZnF zinc chromate (ZnCrO zinc silicate (ZnSiO zinc oxalate (ZnC O zinc arsenate (Zn (AsO The proportion of zinc or the zinc compounds of the charge is preferably 05-10 percent by weight of zinc, zinc oxide, or the zinc salts above. It is also possible to use mixtures of zinc and zinc oxide or zinc and zinc compounds. The proportions of these mixtures are especially -90 percent by weight of zinc and 90-10 percent by weight of zinc oxide and preferably 40-60 of zinc and 60-40 percent by weight of zinc oxide, zinc oxide being an example of the zinc compounds. The proportions of the mixture of zinc or zinc compounds and the cool gas forming substance e.g. waxes are especially 10-90 or preferably 30-70 percent by weight of zinc or zinc compounds and -10 or 70-30 percent by weight of the cool gas forming substance. It is also possible to use other proportions of zinc or zinc compounds of the charge, such as 1-10 percent by weight, 1-6 percent by weight or 2-4 percent by weight of zinc or zinc compounds, such as ZnO and ZnS with the same elfect.

The second or relatively cool gas forming substance invariably contains a substantial amount of carbon i.e. about 30% by weight or more. Best results have been obtained using wax as a second substance, preferably paraffin (approximately 85% carbon) having a melting point between 50 and C. microcrystalline wax e.g. Mobilwax 2305 currently produced by the Mobil Oil Co., ozokerite wax having the same or higher melting point or mixtures thereof. However, examples of other very suitable materials are:

Alkyd resin paint (approximately 70% carbon), for example China-Lack currently produced by Dorch, Backsin and Co., of Gotheburg, Sweden;

Plastic, polyethylene, cellulose acetate, nylon, etc.)

Cellulose (approximately 40% carbon);

Celluloid (approximately 30% carbon);

GreaseAny lubricating grease such as petroleum jelly (e.g. petrolatum), a petroleum or synthetic lubricating oil thickened with a metal salt of fatty acid such as aluminum palmitate, calcium palmitate or stearate, etc. or an oil thickened with a bentonitic clay and commonly used in lubricated ball valves. Other waxes such as ceresin and beeswax. Automobile undercoating compositionse.g. underseal produced by the Minnesota Mining and Manufacturing Company.

When the Wax is used, it has been found that in smaller calibre guns, the lower the melting point of the wax, the more effective it is; however, it is difiicult from a practical point of view to use a wax having a melting point below 50 C.

On combustion of the charge the following reaction is typical of what occurs to the second substance:

(1) Decomposition of the molecules into their components;

(2) Absorption of heat from the charge by reducing the CO and steam in the charge to CO and H It is possible that the organic substances mentioned above also reduce wear by mechanically protecting the barrel from the hot combustion gases. It is very difiicult to be certain what does exactly occur on firing, but the reduction in wear due to the presence of these substances is significant.

In application of the first and second substances to cartridges, it is preferred that the materials be utilized in combination, as for example, a dispersion of the first substance in a layer of the second cool gas forming substance. Very small amounts of the first substance have a beneficial effect while too large an amount may have an adverse effect on the propellant power obtainable in a cartridge of a certain size. Generally, the first substance should constitute between 0.05-20% by weight of the propellant charge, and more preferably should be present between 0.5% and 10% by weight of the charge. The type propellant used introduces only minor variations in test results and the stated percentages are therefore applicable to any conventional single, double, or triple base powder.

It has been found that an obvious effect also is obtained by using the first substance according to the lower limit on the assumption that the substance is applied on a cartridge fabric, said fabric being placed within the case around the propellant charge. When directly coating the inside of the case with the first substance in combination with the second substance, the coating will hardly produce any effect, depending on the high thermal conductivity of the case preventing a sufficient fast combustion of the coating in connection with the firing. If it nevertheless of practical economical and technical reasons is desirable to place the coating directly on the inside of the case an effect can be obtained if the quantity of the coating on the upper part of the case is increased to at least 0.1% by weight of the charge and preferably to at least 1% by weight of the charge according to the dimensions of the gun, in order to obtain reasonable effect. This can be explained from the fact that the lower part of the coating produce the necessary thermal insulation.

It is diflicult to establish a fixed rule by which the optimum amount of second substance can be ascertained. There is a minor but somewhat insignificant effect with very thin layer thicknesses, but the effect increases substantially when the layer thickness reaches a certain value. Good results have been obtained by applying a layer in a sufiicient thickness of the second substance to the outer surface of the propellant charge, or on its container, preferably on the inner surface of said container or to the inner surface of the cartridge case.

The part of the layer adjacent the front part of the charge is more effective than the part of the layer adjacent the rear end of the charge; in fact, if the layer extends the whole length of the charge, the rear half of the layer a certain extent, laminar. Consequently, if the first substance is uniformly dispersed through the charge a substantial part of the substance in the center of the charge is carried by the propellant gases past the part of the barrel where maximum wear normally occurs. Therefore, to obtain a greater effect, additive materials are advantageously arranged so that they surround the charge. Also, it is better to maintain the additives and charge separate since this enables the additives to be simply and cheaply adapted to existing cartridges so that they incorporate the invention. Still another reason is that the additives may have a slightly deleterious effect on the stability of the propellant.

The preferred form of the invention is illustrated in FIGURE 1 wherein a cartridge is shown having a metal case 20, propellant charge 24 comprised of propellant strips as is well known, and a projectile 28. Surrounding charge 24 is a textile wrap 32 which may be of any suitable material such as rayon (preferred) cotton, silk, or other conventional materials. The upper section of wrap 32 has a plurality of vertical slits 36 shown therein through part of its length which form flaps 40 as shown in FIGURE 2. Flaps 40 are adapted to be folded in overlapping manner over the upper surface of propellant charge 24.

Textile 32 is coated, or coated and impregnated with an additive layer 44 composed of powdered tungsten oxide has little effect; and it is the front half, especially the 7 front /3, and particularly the front which has most effect in absorbing heat from that part of the propellant gases which cause the barrel Wear. In heavier guns in which the time for the projectile to travel down the barrel is relatively long, for example 7 /2 cms. guns, the part of the substance beyond the front /3 of the charge is fairly effective, especially when using the first substance and in cartridges for such guns the substance should preferably surround at least the front half, and preferably the front /6 of the charge.

Generally speaking the higher the proportion of carbon, the more effective a given layer thickness is. However, some substances react with the propellant gases more rapidly than other substances. Thus, a substance which has a large carbon content and which reacts slowly may have even less effect than a substance which has a lower carbon content but which reacts more rapidly. However, the following empirical formula for determining the minimum layer thickness has proved to be satisfactory for substances such as those mentioned above:

where C is the calibre of the firearm in cms.; and cm. refers to the area of the layer. The weight of the second substance, such as those mentioned above, which surrounds the front third of the charge should be between 0.05% and advantageously between 0.5% and 10%, of the weight of the total propellant charge.

The formula given above may be expressed more generally so that it applies to all substances as follows:

30 /C gram calories per sq. cm. of layer surfacethat is the substance is such that in reacting with the propellant gases it absorbs 30 gram calories per sq. cm. of the layer surface.

The first substance may be dispersed by mechanical mixing throughout the propellant charge. For example, good results have been obtained by dispersing AlF 3H O (about 1% of the charge weight) throughout the charge of a 37 mm. gun. However, surprisingly good results have been obtained by dispersing the first substance in fine particles throughout the second substance and applying the mixture in a continuous layer around the charge, either directly on the charge, on fabric covering the charge, or on the inner wall of the case. The primary reason for maintaining the additives and charge separate is that the gas flow in the barrel on combustion of the charge is to (W0 dispersed in parafifin wax (melting point approximately 0), preferably 1 part by weight of wax to 2 parts by weight of tungsten oxide. It is preferred that the latter have the texture of talc since smaller particles have generally provided better results for all first substances. In a mm. gun wherein conventional triple base powder composed primarily of nitrocellulose, nitroguanidine and nitroglycerine (calorific value 850) was employed, it was found that optimum results were obtained utilizing additives constituting 3% by weight of the propellant charge.

The additive coating is prepared by melting the wax and thereafter mixing with powdered tungsten oxide. Thereafter, the coating is applied to the fabric in the desired thickness and permitted to cool. The thickness ratio of the top and bottom portions of layer 44 is approximately 3 to l. The thickness of layer 44 applied to flap sections 40 is substantially the same as the maximum thickness along the sides of the charge.

Coated fabric 32 which is preferably one-half to fivesixths the length of the charge, may be wrapped around the strips of charge 24 or it may be held in position in the cartridge as the propellant material is poured in. Thereafter flaps 40 are folded over and projectile 28 is placed on top of the flaps as shown in FIGURE 1.

As thus applied to the charge the additive coated fabric affords the following advantages:

(1) It positions the thicker portion of layer 40' around the upper part of charge 24 where it will offer optimum performance as previously explained;

(2) It has been found that with coated flaps 40, better results may be obtained than when no flaps are used. It is believed that this effect results from the flaps opening on combustion of the charge and extending forwardly to v liberate the additive material into the forward portion of the case, and in some cases directly into the critical portion of the barrel next to the firing chamber where erosion is normally greatest thereby exposing the latter to additives in a more concentrated form than the additive material along the side of the charge which is delivered to the barrel;

(3) The tapered cross section of layer 44 along the length of charge 24 locates the additive material so that it will be substantially uniformly consumed or liberated from the charge throughout the length of the latter.

If desired, fabric 32 may be secured to the inner wall of the case by glue or other suitable means so as to retain the coated fabric in position.

In FIGURE 4 the arrangement of first and second substances to the charge is the same as that described in connection with FIGURE 1 however, layer 44 is covered with a paper layer 48 or other suitable combustible material for the purpose of further protecting the first and second substances from the effects of heat or vibrations.

In FIGURE is shown a cartridge having a case 52, charge 56, and projectile 60. An additive layer 64 embodying a first and a second substances dispersed therein, is positioned around the charge on the interior surface of casing 52. Adjacent the interior surface of the additive layer 64 is an optional sheet 68 of suitable combustible material, e.g., paper, Celluloid, nitrated cotton, wax paper, thin fabric, etc. Layer 64 extends along a substantial length of the case to a point closely adjacent the lower portion of projectile 60. The advantage of this is that the additive material will be made immediately available in highly concentrated form to protect the portion of the barrel usually eroded most severely. Thus, in all embodiments of this invention it will be understood that it is desirable to locate at least a portion of the additive as close to the forward end of the case as is feasible, or alternately to provide flaps which apparently accomplish this same purpose when the cartridge is discharged. The adhesiveness of the second substance itself will generally be sufficient to hold the additive layer securely in place on the casing wall, particularly where the first substance is dispersed in a layer of cellulose enamel or alkyd resin paint for example.

The material of which layer 68 is composed is selected to afford at least slight cooling eflfect (in the manner of a second substance) when the round is fired, but more importantly it helps retain additive layer 64 in position and also protects it from deteriorating influences. It will be understood that layer 68 is not essential, but desirable where for example, the cartridges may be stored or used in hot climate or transported over rugged terrain.

It may be desirable to additionally protect and maintain the position of the additive material by enhancing the bond between the casing and additive layer 64. This may be accomplished by conditioning the case to receive and hold the additive layer more strongly. Thus, in accordance with the embodiment of the invention shown in FIGURE 5, the area of the inner casing surface to be contacted by layer 64 may be coated with a thin layer of glue or other suitable material to produce a rough surface before additive layer 64 is applied. Or, a thin coarse fabric such as gauze or the like may be applied to the casing inner surface by means of a suitable adhesive for receiving and holding the second substance and dispersed first substance in place.

Alternatively, the first and second substances (e.g. wax and tungsten oxide) may be retained on the case wall by being impregnated into a layer of porous material having interstitially connected pores such as foam or sponge rubber or foam plastic. Also, since the rubber may serve as a coolant substance the first substance may be applied in a slurry to the porous material and dried.

FIGURE 6 illustrates a cartridge similar to that shown in FIGURE 5 with an additive layer 80 disposed on the inner surface of case 84 around charge 88 but without a thin intermediate textile or paper separating the charge and layer 30. Also, layer 80 is of uniform thickness throughout its length.

The following examples illustrate different forms of fixed cartridges embodying the invention for use in 37 mm. anti-tank gun whose barrel is made of chrome alloy steel and wherein the propellant charge is double base powder containing nitroglycerine and having a calorific value of 1150 calories. The charge weighs 220 grams, and it is arranged in strips each 225 x 12 x 0.65 mm. The cartridge cases are, in all the figures 250 mm. long.

8 The cartridge shown in FIGURE 7 comprises a case 100, a charge 104 consisting of strips tied together by string 106, and a layer 110 of powdered vanadium pentoxide dispersed in an alkyd resin paint applied to the upper part of the inner wall of the cartridge case. The vanadium pentoxide constitutes 60% by weight of the layer. The thickness of the layer is 0.5 mm.; its length is 50 mm.; and its weight is 3 grams.

The cartridge shown in FIGURE 8 utilizes, for example aluminium fluoride or other first substance contained in a bag 114 located within textile container 118. The wear reduction obtained with this cartridge is not as great as the wear reduction obtained in the cartridges shown in FIGURE 7, probably because the additive does not surround the charge.

The cartridge shown in FIGURE 9 comprises a case 120, strips 124 tied together by string 128, and an additive layer 132. The first substance, for example pulverulent aluminum fluoride (AlF 3H O) is contained in a plastic ring such as polyethylene for example, located at the upper end of the cartridge case. In this embodiment of the invention the additive layer is relatively thick and short. The increased cross section of the layer enables the gas pressure to readily remove the material from the case into the barrel.

The cartridge of FIGURE is substantially the same as the cartridge of FIGURE 7. The vanadium pentoxide 133 is however not dispersed in an alkyd resin paint but is fixed to the inside of the case by a non-organic or organic adhesive.

The cartridge shown in FIGURE 11 comprises a case 134, a charge 138 contained in a textile bag, and a coating 42 on the upper part of the charge. The coating extends 10 cms. downwardly from the top of the container and consists of a cellulose enamel containing 70% of vanadium pentoxide. The weight of coating per sq. cm. is 50 mgs.

The cartridge shown in FIGURE 12 comprises a case 146, a charge 150 and a length of textile 154 wrapped around the upper part of the strips to form a layer containing the two substances. The textile length so coated with an alkyd resin paint 158 containing powdered aluminium fluoride in about 60% of the weight of the dried layer. The coated length 154 extends 10 cms. downwardly from the top of the propellant. The weight per sq. cm. of the layer is 70 mgs.

Tests were carried on with a mm. automatic cannon in which conventional cartridges and cartridges containing different forms of the first substance mechanically mixed with and dispersed throughout the powder were used. The powder used was 7 hole N-C powder, and the total weight of the charge was 37 grams. The initial muzzle velocity was 840 metres/second and each test consisted of 2 series of firings each of rounds. The cannon was fitted with a removable sleeve in the area between the chamber and the rifled portion of the barrel. After the firing the sleeve was removed and the wear was as ascertained by weighing the sleeve.

First substance Weight reduction Wear in percent in mg.

95. 5 72. 6 14. 9 ll. 3 1% KzT1F5 80.1 60. 9

achieved First How arranged substance Wear in percent 1 A1F33HzO Contained in a propellant foil wrapped around the charge. Foil was 0.8 mm. thick and contained 25% by weight of AlF33H-ZO.

CrFs Contained in a foil wrapped around charge and composed of propellant. Foil was 0.8 mm. thick and contained 20% by weight of CrF M dispersed in varnish (Ferbo-lack) applied to a 0.15 mm. thick Celluloid foil wrapped around the charge. The length of the layer was 10 ms, and 6 grams of M00; was applied to the foil.

NazW04 applied in a layer to 0.15 mm. thick Celluloid foil wrapped around charge. The length of the layer was 10 ems.

A cellulose enamel coating applied to the inner surface of the cartridge container and containing 25 gins/cm. (approximately 70%) of CrFs. The length of the coating was ems.

As a powder dispersed throughout the charge.

Powder 2.5% by weight of the charge.

As a powder dispersed throughout the charge.

Powder 1.2% by weight of the charge.

Contained in a paraffin wax layer on the inside of the cartridge case. The layer was 50 mm. in length and 0.5 mm. in thickness and contained 50% by weight of W0 although 50- 70% has been used successfully. Or instead of W03, Nbz05 was used with equally good results.

Contained in a paraflin wax layer on the inside of the cartridge case. The layer was 50 mm. In length and 0.5 mm. in thickness and contained 40% by weight of ZnO and 60% by Weight of the wax.

Contained in a parafiin wax layer according to the example with W0: and ZnO but with 67% by weight of Zn and 33% by weight of the wax.

Contained in a paraffin wax layer on the inside of the cartridge case. The layer was 50 mm. in length and 0.5 mm. thick, and contained 50% by weight of T3205.

Contained in a paraffin wax layer on the inside of the cartridge case. The layer was 50 mm. in length and 0.5 mm. thick, and contained 50% by weight of 'IiOz.

TiOz 5 Wear without either substance being regarded as 100%.

The following arrangement of the first and second substance in a cartridge for a 3 inch gun reduced the wear in a steel barrel to of what it was previously-that is a reduction of 90% A length of fabric coated with paraffin wax having a melting point of 70 C. was wound once around the front of the tubes of conventional double base nitrocellulose powder containing nitroglycerine housed in a metal case. Powdered tungsten oxide was dispersed in the wax, and constituted 50% by weight of the mixture of wax and tungsten oxide and the weight of the coated textile length was 3% by weight of the charge. Similar tests with nearly equally good results, have been carried out with TiO used in place of W0 in the same amount.

Similar tests with equally good results (less than 10% Wear) have been carried out with a mixture of 40% by weight of ZnO and 60% by weight of wax and 67% by weight of Zn and 33% by weight of wax.

Examples of other forms of the first substance are zirconium oxide ZrO and sodium molybdenum oxide (Na2M0O4).

The first substance reduces barrel wear further from the chamber than does .the second substances. In addition the coolant second substance may cooperate with the first substance by producing an environment more favorable physical and chemical to the formation of an effective temperature and erosion resistant layer. Thus, a cartridge having both substances results in less barrel wear than a cartridge having only one of the substances.

Although it is preferred to use the first and second substances together in a single layer of additive as described above, it is also possible to effect substantial reductions in barrel wear by using either of the materials individually. In FIGURES 1-12 the second substance may be used alone arranged in the cartridge in the manner 10 shown and described for the various additive layer positions and arrangements. The relative amount of :the second substance asa'foresaid, should be between about .05 to 30% of the charge weight for all conventional powders.

Tests using the 37 mm. cartridges, described above, and without the metallic compounds constituting the first substance were carried out. The best results were obtained with a layer of paraflin wax on the inner wall of the case; the layer was 50 mm. long and 0.6 mm. thick; its total weight was 3.5 grams, and the melting point of the wax was 50' C. The wear resulting from this cartridge was 5%that is a reduction in Wear of With the alkyd resin paint without the vanadium pentoxide particles the wear was 30% that is a reduction of 70% with the ce1lulose enamel coating of FIGURE 11 the wear 50%; with the alkyd resin coated textile length of FIGURE 12 the wear was 30%.

For ease of application it is preferable to disperse the first substance in the powder charge when used alone, or to place a quantity of the substance on top of the charge strips allowing some to migrate into the space between the strips. dividual application is the same as used in combination with the second substances.

What is claimed is:

1. For use in a gun barrel, in combination: a single projectile; an explosive charge which when fired produces hot propellant gases for propelling the projectile through the gun barrel; and an additive for reducing gun barrel wear resulting from the firing of such projectile comprising a substance selected from the group consisting of zinc and zinc compounds present in an amount between 0.05 and 20% by weight of the propellant charge to provide on the inside surface of the gun barrel a temporary protection having a high resistance to temperature and wear.

2. The combination as defined in claim 1, in which said substance is uniformly dispersed throughout said charge.

3. The combination as defined in claim 1, in which said substance is concentrated between said charge and said projectile.

4. The combination as defined in claim 1, including a fabric container in which said charge is housed, and having said substance incorporated in a layer on a substantia portion of said fabric container.

5. The combination as defined in claim 1, including a case having said charge located therein, said substance being incorporated as a layer applied to the inner surface of said case.

6. The combination as defined in claim 1, including a fabric length having said substance incorporated as a layer on said fabric length, said fabric length being wrapped around said charge to substantially separate said charge from said projectile.

7. The combination as defined in claim 1, including a case surrounding said propellant charge and a textile sccured to the inner surface of said case and having said substance coated on said textile to retain the position of said substance in said case.

8. The combination as defined in claim 1, including a thin sheet carrier material having said substance applied thereto, said thin sheet carrier material having portions thereof folded over the front end of the charge to be located between the charge and the projectile.

9. The combination as defined in claim 8 wherein said portions are flaps folded over said charge.

10. The combination as defined in claim 1, including a. case having a rough inner surface wherein said propellant charge is located within said case having a rough inner surface and said substance is held on the inner surface of said case.

11. The combination as defined in claim 1, including a layer of material containing a substantial amount of carbon capable of producing relatively cool gas upon firing of said propellant charge wherein said substance is in The amount of first substance used in its in-' 1 l the form of finely divided particles and dispersed within said layer.

12. The combination as defined in claim 11 wherein said carbon material is a wax.

13. The combination as defined in claim 11 wherein the carbon containing material is present in an amount ranging from about 0.05 to 30% of the weight of the propellant charge.

14. A method of reducing gun barrel wear in a firearm when firing a shot having a single projectile and a propellant charge, comprising: introducing into the chamber of the firearm before its discharge a substance for reducing gun barrel wear selected from the group consisting of zinc and Zinc compounds, the amount of said substance introduced being sufficient to provide on the inside surface of the gun barrel a temporary protection having high resistance to temperature and wear, and firing said projectile through said gun barrel by igniting said propellant charge to produce hot propellant gases.

15. The method as defined in claim 14 wherein the zinc compound is zinc oxide.

16. The method as defined in claim 14 wherein the zinc compound is zinc sulfide.

17. The method as defined in claim 14 wherein the Zinc compound is zinc phosphate.

18. The method as defined in claim 14 wherein the zinc compound is zinc carbonate.

19. The method as defined in claim 14 wherein the zinc compound is Zinc fluoride.

14 wherein the 14 wherein the 14 wherein the References Cited by the Examiner UNITED STATES PATENTS 943,589 12/09 Bent 149-38 1,1 87,779 6/ 16 Patten. 1,316,786 9/19 Gerli 10243 1,336,463 4/20 Henning 10298 1,957,935 5/34 Burke 102-43 2,131,353 9/38 Marsh 102-98 2,159,234 5/39 Taylor 10-2-98 2,299,464 10/42 Cotfman 10239 X 2,301,043 11/42 Hardy 10239 X 2,309,978 2/ 43 Pratt 10239 2,604,391 7/52 Taylor-Hutchison 102-98 2,637,274 5/ 5 3 Taylor et al 10298 2,701,524 2/55 Van Dine 10238 2,744,816 5/56 Hutchison 10238 2,989,388 6/61 Toulmin 14938 SAMUEL FEINBERG, Primary Examiner.

SAMUEL BOYD, Examiner. 

1. FOR USE IN A GUN BARREL, IN COMBINATION: A SINGLE PROJECTILE; AN EXPLOSIVE CHARGE WHICH WHEN FIRED PRODUCES HOT PROPELLANT GASES FOR PROPELLING THE PROJECTILE THROUGH THE GUN BARREL; AND AN ADDITIVE FOR REDUCING GUN BARREL WEAR RESULTING FROM THE FIRING OF SUCH PROJECTILE COMPRISING A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ZINC AND ZINC COMPOUNDS PRESENT IN AN AMOUNT BETWEEN 0.05 AND 20% BY WEIGHT OF THE PROPELLANT CHARGE TO PROVIDE ON THE INSIDE SURFACE OF THE GUN BARREL A TEMPORARY PROTECTION HAVING A HIGH RESISTANCE TO TEMPERATURES AND WEAR. 